There is a huge drop in performance as you get away from the ss. The inner tech of most bats are made to maximize
ss trampoline. As you get away from the ss, the reaction of the barrel is much less...whether you misshit towards the
endcap or handle, will be less than the ss. Thats why when they do compression test, they do it at the ss.
The BPF is only what the bat is allowed to get to. Now, the key is that when you play with the inner tech, you can make
the outer composite thinner and hotter...and the inner tech keeps the bat from going over the limit. Thats why you get
bats that are hotter out of the wrapper than others
The inner and outer combined result in a bat that doesn't exceed the 1.20 bpf standards.. From what I understand, the velocity of the ball in the test is rather high which may be done to simulate a "big" and more dangerous to the defense swing.. The inner basically deadens the bat to the 1.20 standards and protects the outer from over deflecting. If the inner wasn't there, the trampoline effect of the outer would be huge, but the composite wouldn't survive at all from the deflection.
My opinion is that many dual wall bats "help" with out of range (as compared to the 1.20bpf test) bat/ball contacts and to outperform "standard" single wall bats in those sub optimal conditions, i.e. the 1.20bpf doesn't restrict how hot a "slower" bat/ball collision or sub optimal sweet spot contact can be, it is only designed to restrict the highest velocity contacts. I genuinely believe that the older and stronger that a player gets, the less and less difference bats make. just my .02